An electron spin resonance study was made of (100)Si/SiOx/ZrO2 and (100)Si/Al2O3/ZrO2 stacks with nm-thin dielectric layers, grown by using the atomic layer chemical vapor deposition method at 300C. This revealed that Si dangling-bond type centers, Pb0, Pb1, were prominent defects at the (100)Si/dielectric interface in both types of structure. This indicated that the as-deposited (100)Si/Al2O3 interface was basically (100)Si/SiO2-like. However, as shown by the spectroscopic properties of the Pb0 and Pb1 defects, the interfaces were found in an enhanced (less-relaxed) stress state that was usually characteristic of low-temperature Si/SiO2 fabrication. The thermal behavior was tested by subjecting the sample stacks to heat-treatment in vacuum or O2 ambients. Based upon the Pb0, Pb1 criterion, it was found that standard thermal Si/SiO2 interface properties were approached upon annealing at above 650C in vacuum; in the case of Si/SiOx/ZrO2. On the other hand, an O2 ambient was required for Si/Al2O3; thus indicating that the initial interface was too abrupt to permit thermal interfacial rearrangement without growth of an additional SiOx interlayer. A minimal SiOx interlayer thickness (0.5nm) appeared to be needed. Thus, Si/high-k metal oxide structures could be given device-quality interfaces by a sub-nm SiOx interlayer.

Defects at the Interface of (100)Si with Ultrathin Layers of SiOx, Al2O3 and ZrO2 Probed by Electron Spin Resonance. A.Stesmans, V.V.Afanasev: Journal of Vacuum Science & Technology B, 2002, 20[4], 1720-5